Final answer:
Cross-sectional designs are utilized for observational studies at a specific time point, while quasi-experimental designs attempt to determine causation without random assignment of participants, commonly used when randomization is not feasible.
Step-by-step explanation:
When discussing cross-sectional designs and quasi-experimental designs, we are referring to methodologies used in the social sciences for conducting research. A cross-sectional design is a type of observational study that analyzes data from a population, or a representative subset, at a specific point in time. Instead of following subjects over some time, cross-sectional studies take a 'snapshot' approach to research. On the other hand, a quasi-experimental design is a research strategy that attempts to establish cause-and-effect relationships but lacks random assignment of participants to control and experimental groups. Quasi-experimental designs are commonly used when randomization is impractical or unethical. In practice, researchers use these designs to infer causation despite potential limitations in controlling for all possible confounding variables.